Electric motor drive systems, such as those used in hybrid and electric vehicles (HEVs), typically include an alternating current (AC) electric motor, a power converter and a direct current (DC) power source, such as a storage battery. The power converter typically includes an inverter module that coverts energy from the power source to drive the electric motor. Motor windings of the AC electric motor can be coupled to inverter sub-modules of the inverter module. Each inverter sub-module includes a pair of switches that switch in a complementary manner to perform a rapid switching function that convert the DC power to AC power. This AC power drives the AC electric motor, which in turn drives a shaft of HEV's drivetrain.
One drawback of many conventional electric motor drive systems is that the electronics (e.g., transistors such as IGBTs) in the inverter module are enabled and continue switching even when the commanded torque is zero (i.e., no torque is commanded from the AC electric motor). In other words, the switches of inverter module are active not only when torque is required from the motor, but also when torque is not and will continue switching even when no torque is required from the motor. This unnecessary switching can result in unnecessary power loss, which reduces efficiency of the system.
It would be desirable to provide improved methods, systems and apparatus for reducing electrical power losses in electric motor drive systems that include an electric machine and inverter module. It would also be desirable to improve efficiency of electrical motor drive systems, and to improve the usage of direct current (DC) power source(s). For instance, it would be desirable to provide methods, systems and apparatus for reducing or minimizing power loss due to unnecessary switching within an inverter module. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.